Redesign make_ext4fs to incrementally generate ext4 images
Allows passing a base fs mapping file through -d which preserves the
location of those mapping in existing files
Internal Design Doc: go/incremental-ext4
BUG: 26839493
Change-Id: I05e296693429d39466d257d1d0a3daf00510dc26
Signed-off-by: Mohamad Ayyash <mkayyash@google.com>
diff --git a/ext4_utils/extent.c b/ext4_utils/extent.c
index 1900b10..42ddd97 100644
--- a/ext4_utils/extent.c
+++ b/ext4_utils/extent.c
@@ -5,7 +5,7 @@
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
- * http://www.apache.org/licenses/LICENSE-2.0
+ * http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
@@ -72,23 +72,43 @@
}
static struct block_allocation *do_inode_allocate_extents(
- struct ext4_inode *inode, u64 len)
+ struct ext4_inode *inode, u64 len, struct block_allocation *prealloc)
{
- u32 block_len = DIV_ROUND_UP(len, info.block_size);
- struct block_allocation *alloc = allocate_blocks(block_len + 1);
+ u32 block_len = DIV_ROUND_UP(len, info.block_size), prealloc_block_len;
+ struct block_allocation *alloc;
u32 extent_block = 0;
u32 file_block = 0;
struct ext4_extent *extent;
u64 blocks;
- if (alloc == NULL) {
- error("Failed to allocate %d blocks\n", block_len + 1);
- return NULL;
+ if (!prealloc) {
+ alloc = allocate_blocks(block_len + 1);
+ if (alloc == NULL) {
+ error("Failed to allocate %d blocks\n", block_len + 1);
+ return NULL;
+ }
+ } else {
+ prealloc_block_len = block_allocation_len(prealloc);
+ if (block_len + 1 > prealloc_block_len) {
+ alloc = allocate_blocks(block_len + 1 - prealloc_block_len);
+ if (alloc == NULL) {
+ error("Failed to allocate %d blocks\n",
+ block_len + 1 - prealloc_block_len);
+ return NULL;
+ }
+ region_list_append(&prealloc->list, alloc->list.first);
+ free(alloc);
+ }
+ alloc = prealloc;
}
int allocation_len = block_allocation_num_regions(alloc);
if (allocation_len <= 3) {
reduce_allocation(alloc, 1);
+ // IMPORTANT: reduce_allocation may have changed allocation
+ // length, otherwise file corruption happens when fs thinks
+ // a block is missing from extent header.
+ allocation_len = block_allocation_num_regions(alloc);
} else {
reserve_oob_blocks(alloc, 1);
extent_block = get_oob_block(alloc, 0);
@@ -183,7 +203,7 @@
struct block_allocation *alloc;
u8 *data = NULL;
- alloc = do_inode_allocate_extents(inode, len);
+ alloc = do_inode_allocate_extents(inode, len, NULL);
if (alloc == NULL) {
error("failed to allocate extents for %"PRIu64" bytes", len);
return NULL;
@@ -205,9 +225,26 @@
struct block_allocation* inode_allocate_file_extents(struct ext4_inode *inode, u64 len,
const char *filename)
{
- struct block_allocation *alloc;
+ struct block_allocation *alloc, *prealloc = base_fs_allocations, *prev_prealloc = NULL;
+ // TODO(mkayyash): base_fs_allocations is sorted by filename, consider
+ // storing it in an array and then binary searching for a filename match instead
+ while (prealloc && prealloc->filename != NULL) {
+ if (!strcmp(filename, prealloc->filename)) {
+ break;
+ }
+ prev_prealloc = prealloc;
+ prealloc = prealloc->next;
+ }
+ if (prealloc) {
+ if (!prev_prealloc) {
+ base_fs_allocations = base_fs_allocations->next;
+ } else {
+ prev_prealloc->next = prealloc->next;
+ }
+ prealloc->next = NULL;
+ }
- alloc = do_inode_allocate_extents(inode, len);
+ alloc = do_inode_allocate_extents(inode, len, prealloc);
if (alloc == NULL) {
error("failed to allocate extents for %"PRIu64" bytes", len);
return NULL;
@@ -222,7 +259,7 @@
{
struct block_allocation *alloc;
- alloc = do_inode_allocate_extents(inode, len);
+ alloc = do_inode_allocate_extents(inode, len, NULL);
if (alloc == NULL) {
error("failed to allocate extents for %"PRIu64" bytes", len);
return;